The present invention relates to a pulse measurement system and, more particularly, to a pulse number measurement system included in an electronic sphygmomanometer.
Recently, an electronic sphygmomanometer has been developed, which includes a pulse measurement system for measuring a pulse number through the use of pulse interval data derived from the Korotkoff sound detection device. An example of the electronic sphygmomanometer having such a pulse measurement system is disclosed in a copending application Ser. No. 463,475, entitled "ELECTRONIC SPHYGMOMANOMETER WITH VOICE SYNTHESIZER", filed on Feb. 3, 1983 by Ryuichi Miyamae and Haruo Yasuda, and assigned to the same assignee as the present application.
In the conventional pulse measurement system included in the above-mentioned electronic sphygmomanometer, each pulse interval data is stored in a memory (RAM), and the mean interval value is calculated through the use of the thus stored plurality of pulse interval data before obtaining the pulse number information. Accordingly, if the measurement accuracy is desired to be enhanced, the sample number of the pulse interval data stored in the RAM should be increased. Therefore, the conventional pulse measurement system needs a RAM of large memory capacity.
Accordingly, an object of the present invention is to provide a novel pulse measurement system in an electronic sphygmomanometer.
Another object of the present invention is to enhance the measurement accuracy of the pulse number with a memory device of small memory capacity.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a plurality of memory sections are included in a memory device (RAM) for storing the pulse interval data. When new pulse interval data is obtained, the new data is compared with the previously determined maximum interval data or the minimum interval data which have been stored in the RAM. When the new pulse interval data is smaller than the maximum interval data, the previously determined maximum interval data is changed to correspond to the new interval data. When the new pulse interval data is larger than the previously determined minimum data, the minimum data is changed to correspond to the new interval data. The thus updated pulse interval data are used to calculate the pulse number.
In a preferred form, the RAM includes at least three memory sections A, B and C. The memory section A stores the previously determined maximum interval data, and the memory section C stores the previously determined minimum interval data. As already discussed above, the maximum data and the minimum data stored in the memory sections A and C are updated when new pulse interval data is obtained. The memory section B stores the sample data which fulfills the condition A.gtoreq.B.gtoreq.C.
When the pulse interval data has been measured a predetermined number of times, the measurement operation is completed and the sample data stored in the memory section B is used as the center value. That is, the sample data stored in the memory section B is applied to a calculation circuit which calculates the pulse number information.